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Need help in determining if this 377 Cubic inch will work in boat

Old 08-25-2004, 11:01 PM
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Default Need help in determining if this 377 Cubic inch will work in boat

Need help in Cam selection and if this is a good 377 cubic inch motor. Will be running in a 19 foot stern drive boat no more than 5500 rpms with stock 4 inch GLM aluminum manifolds. Need a good cam !

Here is my setup:

1) 4.155 bore cast iron GM Block w/ 9.000 deck height, simese holes plugged and the six 3/4 water galley holes plugged then redrilled to 1/4 inch. BILLET STEEL SPLAYED main caps.

2) Eagle Forged Steel Crankshaft 3.480 stroke w/ Internal balancing.

3) Eagle 4340 Forged Steel 6.125 Inch H-Beam 7/16 Cap Screw Connecting Rods w/ Bronze Bushings.

4) Childs & Albert 1/16-1/16-3/16 Plasma Moly File Fit Rings. Top Ring .016 End Gap & Second Ring .018 End Gap.

5) Clevite Coated Cam, Main, & Rod Bearings.

6) JE 4.155 Forged Pistons w/ -22cc Dish, 1.125 Pin Height, Oil Rails, Double Sprial Locks, & JE Tool Steel 2.750 Wrist Pins.

7) Air Flow Research Cylinder Heads. Fulley Professionally Ported Heads using Super Flo Flow Bench. Epoxy Was Used In Ports to Increase Flow Rates (80hours porting and flow work spent) (60cc Combustion Chamber) 2.100/1.625 Manley Race Master Valves, Competition Cam Dual 1.550 Diameter Valve Spring w/ .824 I.D. 162lbs Closed @1.900 Installed V/S Height & 484lbs @1.250--Coil Bind 1.085. Competition Cam Retainers , Hardened Rocker Studs, Guide Plates, and Positive Valve Seals

8)Competition Cam Hardened Tip Moly Heat Treated Pushrods 7.800 length

Any opinion on engine setup and a cam selection, using normal 4 inch thru hull exhaust (for now).
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Old 08-25-2004, 11:13 PM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

My 383 has a Comp Cams XM276HR. Its a hydraulic roller with 224/230 @.050 with .503/.510 lift. Good cam to 5500 RPM. The motor idles pretty good with 14 in of vacuum. What kind of flow numbers did the heads post? My ported trick flows came in at 258 cfm at .500. You may even be able to get them to cut a 230/236 extreme marine cam which will probably peak closer to 5900. Those springs seem pretty heavy. Are you going the route of a solid roller with real aggressive ramps?
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Old 08-26-2004, 07:36 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

Thanks for replying as I am looking for help.
As for as cam selection was looking to stay hydraulic for now (same with exhaust). Not sure flow numbers of heads, but beleive they where several hours of work down to them to help increase. I also agree with the heavy springs. Can I get away with using them? My old more semi stock 350 I used the comp cam XM 270, 226/236 and .480/489 lift (worked well). Should I try using same again or try and get a little more lift. Will those JE pistons with the long rods work for longevity ? Any other suggestions as I am learning about this and have picked up much good info from this site?
Thanks !!
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Old 08-26-2004, 07:53 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

Some suggestions:
1) The 6.125 rod on a deck of 9.00” nets you a very short CH of 1.135” yielding a tight ring stack, high in the bore, with the oil ring well into the pin. In this application the high rod ratio is of no real advantage. Consider running a 5.7”/ 6” rod.
2) Do you have flow #’s for the heads? The AFR s have some of the best I/E ratios of any 23* head. Chances are you are above 75%, combine that with the longer rod, and you are definitely in the market for a custom grind with a smaller split than the shelf grinds offer. Correct cam selection is dependant on flow #s
3) I would measure for pushrod length and order them accordingly as the block has been decked altering the geometry.
4) I would not consider running those springs. They are not for Hyd applications Chances are very slim they would be compatible with your cam even if it were a solid. Order the springs with your cam and install them to the proper pressure.
Best of luck
Bob

Last edited by rmbuilder; 08-27-2004 at 06:05 PM.
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Old 08-26-2004, 08:13 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

RMBuilder and Others - Thanks for the immediate Help !! (as I need it)
With much of whats said, can I stay with the rod length (dont want to have to go back inside motor), and will the JE pistons (and the setup) be allright for longevity ?
Where and who should I call for custom grind (any best suggestions) and what is the best info I should give them for their determination of proper grind.
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Old 08-26-2004, 08:28 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

I was kind of wondering why such a long rod. I think for 5500-RPM you're better off with a 5.7" and a little more ring seperation.

Roby
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Old 08-26-2004, 09:09 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

Robyw1,
Correct. There are to many negatives regarding reliability running the 6.125” rod in this build.
1. The top ring land is to high in the bore narrowing the ring land and elevating ring/land temp.
2. The oil ring is in the pin area.
3. Long rods move the HP peak closer to the torque peak narrowing the power band. This is fine in a 5 speed or speedway engine, but where a broad, flat power curve is desirable (marine application) it is not an advantage.
4. As far as the long rod reducing cylinder wall loading, reciprocating mass (say 5 grams @ 5500 rpm) has far more effect on major/minor axis thrust surface load than a few degrees of rod angle.
Bob

Last edited by rmbuilder; 08-27-2004 at 06:09 PM.
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Old 08-26-2004, 09:34 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

The end gaps are insufficient for a marine engine @ .016/.018, especially with the top ring land width reduced and the resulting elevated temps. Check the table below for ring gaps for JE Pistons.
http://www.jepistons.com/pdf/piston_instrc4032.pdf
It appears that this was originally a drag build, not endurance, given the large bore short stroke, long rod config. I would seriously consider the reliability factors before you purchase this motor and run it as a marine/endurance engine in its present spec.
Bob
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Old 08-26-2004, 11:09 AM
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Default Re: Need help in determining if this 377 Cubic inch will work in boat

IF however he decides to use this engine in a marine environment then a closed cooling system is a MUST. This is because any corrosion will quickly reduce the already limited and very hot water that flow through those steam holes. Also I don't know if these heads are aluminum but if so you can't be running salt water through them. I think for my money I would have gone 350 block 400 crank instead of the opposite in which this engine is.

Roby
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